Landau criterion in a bose-condensed sodium gas

• Analysis of the speed of sound for a sodium gas trapped by a harmonic oscillator.
• Deduction of the critical speed for superfluidity.
• Comparison of the theoretical results against experiments.

In light of the experimental evidence for the existence of a superfluidity region in a Bose-condensed sodium gas a theoretical model is put forward and with it the corresponding threshold velocity for the emergence of superfluidity is deduced. The prediction for the speed of sound and for the critical speed stemming from the present model will be compared against the extant experimental results. In addition, this prediction coincides also with previous calculations stemming from numerical simulations.